title: Gender differences in blood pressure-related hypoalgesia in a general population: the Tromsø Study.
abstract: An inverse association between resting blood pressure (BP) and acute pain sensitivity is well documented. Whether BP-related hypoalgesia differs by gender is unclear from prior work. Whether it increases proportionally with BP throughout the full BP range is also unknown. We examined BP-related hypoalgesia in a general population sample (n = 10,371, aged 30-87) of equal gender distribution reflecting the extremely low through hypertensive BP range. Resting BP was assessed and individuals participated in a standardized cold pressor test, providing pain ratings every 9 seconds. For systolic BP (SBP), a significant SBP × Gender interaction was observed on mean pain ratings (P < .001). Females displayed significant BP-related hypoalgesia (P < .001), with males showing a 38% smaller effect (P < .001). A similar DBP × Gender interaction was also observed (P < .05). Spline regression indicated a significant (P < .001) change in slope of the SBP-pain association at 140 mmHg. Among individuals with lower resting SBP (<140/90), increasing hypoalgesia with increasing SBP levels was observed (P < .001), with no further increases in those with higher BP (≥140/90; P > .10). This is the first large-scale study to confirm past results suggesting that BP-related hypoalgesia differs by gender; that is, females exhibited greater hypoalgesia. BP-related hypoalgesia appears subject to ceiling effects in the hypertensive BP range.
  
  
  CONCLUSIONS
  Females show greater BP-related hypoalgesia than males, highlighting gender differences in endogenous antinociceptive systems. Extent of BP-related hypoalgesia does not increase further once resting pressures reach the hypertensive range, suggesting persistent maximal demands on these antinociceptive systems among hypertensive individuals.
authors.affiliation: Department of Anesthesiology, Division of Emergencies and Critical Care, Oslo University Hospital, Rikshospitalet, Oslo, Norway. r.b.olsen@medisin.uio.no
authors.forename: Roy Bjørkholt
authors.initials: RB
authors.lastname: Olsen
authors.forename: Stephen
authors.initials: S
authors.lastname: Bruehl
authors.forename: Christopher Sivert
authors.initials: CS
authors.lastname: Nielsen
authors.forename: Leiv Arne
authors.initials: LA
authors.lastname: Rosseland
authors.forename: Anne Elise
authors.initials: AE
authors.lastname: Eggen
authors.forename: Audun
authors.initials: A
authors.lastname: Stubhaug
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001794:Blood Pressure; D005260:Female; D006801:Humans; D006973:Hypertension / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009664:Norway; D017288:Pain Threshold / Q000502:physiology*; D012727:Sex Characteristics